Arc runner between stationary contacts

ABSTRACT

A high current capacity molded case circuit breaker having arcing and main contacts and an arc chute to receive and extinguish arcs drawn between the arcing contacts is provided with a magnetic arc runner disposed between the stationary sections of the main and arcing contacts to direct arcs that initiate at the stationary main contact onto the stationary arcing contact.

[ Jan. 8, 1974 1 ARC RUNNER BETWEEN STATIONARY CONTACTS [75] Inventor:Carl E. Gryctko, Haddon Heights,

[73] Assignee: I-T-E Imperial Corporation,

Philadelphia, Pa.

[22] Filed: July 27, 1972 [21] Appl. No.: 275,523

3,582,966 6/1971 Strobe] ZOO/144 R Primary ExaminerRobert S. MaconAtt0meySidney G. Faber et al.

[57] ABSTRACT A high current capacity molded case circuit breaker havingarcing and main contacts and an arc chute to [52] US. Cl. 200/146 R,ZOO/147 R receive and extinguish arcs drawn between the arcing [51] Int.Cl. HOlh 33/12 contacts is provided with a magnetic arc runner dislField ar h /14 147 posed between the stationary sections of the main andZOO/147 B arcing contacts to direct arcs that initiate at the stationarymain Contact onto the stationary arcing [56] References Cited contact.

UNITED STATES PATENTS 3,171,936 3/1965 Jencks et a1. 200/147 R 9 Claims,3 Drawing Figures 1 1 1" F] o 0 1 I o] 27/ 0 24/ m3: 7

i r" //'u I 'I i i 23 L. 1 l 11 .1 r a 1 .J 1 T 7 1 m w W 0 .1 G 0 L 7 wr 1 K? L 1 1 4 1 e1 1 1 1 I 13/ SHEEI 1 OF 2 g WWW ARC RUNNER BETWEENSTATIONARY CONTACTS This invention relates to molded case circuitbreakers in general and more particularly relates to means fortransferring arcs from the stationary main contacts to the stationaryarcing contact.

Circuit breakers of high current ratings are provided with separatearcing and main contacts. In moderately high current rated breakers,arcing is confined to the arcing contact and aspaced plate type of chuteis provided to receive and extinguish arcs formed on the arcing contact.However, for circuit breakers of very high current ratings, say 2,000amperes and more, some initial arcing often takes place at one or moreof the main stationary contacts. This condition has proven to be veryserious in that there is normally no arc extinguishing means in thevicinity of the main contacts, so that arcs formed thereon hang on foran excessive period of time causing severe pitting of the main contacts.

In accordance with the prior art, are runners have usually beenassociated with the arcing contacts, usually positioned more deeply inthe arc chute than the arcing contacts. For those structures in whicharcing occurred at the main contacts, methods other than are runnerswere employed to prevent arcs at the main contacts from being madeinterrupting points of the circuit. To accomplish this, the prior arthas utilized insulating shields positioned between the main contacts andthe plates of the arc chute. With such a construction, if arcingoccurred at the main contacts, this arcing was blocked from proceedinginto the arc chute, but was expected to extinguish if and when arcingwastransferred to the arcing contact and its associated runner.

For very high current rated breakers, it has been found that arcing onthe main contact does not always transfer to the stationary arcingcontact, and if the main contacts are insulated from the arc chute,excessive damage will occur as a result of the are hanging on to themain contacts. The instant invention solves this problem by providing amagnetic arc runner between the main contacts and the arcing contact, sothat arcs established at the main contacts are attracted to the magneticarc runner which directs these arcs to the arcing contact where the.arcs enter the arc chute associated with the arcing contact and areextinguished.

Accordingly, a primary object of the instant invention is to providenovel means for minimizing arcing time at the main contacts of a circuitbreaker.

Another object is to provide means of this type for directing arcs fromthe main to the arcing contacts.

Still another object is to provide a magnetic are runner positionedbetween the stationary main and arcing contacts to facilitate transferof arcs, established on the ,main contacts, to the arcing contact.

These objects as well as other objects of this invention will becomereadily apparent after reading the following description of theaccompanying drawings in which:

FIG. 1 is a longitudinal cross-section of a multipole circuit breaker,showing the elements of one pole thereof, including the arc runner ofthe instant invention.

FIG. 2 is an enlarged side elevation of the line terminal strap of FIG.1, together with the stationary contacts and arc runner mounted thereon.

FIG. 3 is a plan view of the terminal strap of FIG. 2, looking in thedirection of arrows 3-3 of FIG. 2.

Now referring to the figures. Multipole circuit breaker 25 includes amolded housing constructed of base 26 and removable cover 27 abutting atinterface 28. The main current path through each pole of circuit breaker25 is identical and consists of load terminal strap 61 connected by aplurality of flexible conductors 120, 121*to the groups of movable maincontacts 103, 107 engaged with stationary main contacts 231, 232,respectively, extending across line terminal strap 136 and brazed orotherwise secured to the upper surface thereof.

Movable arcing contact 101, mounted at the forward end of arm 112, isengageable with stationary arcing contact 233, mounted on the uppersurface of terminal strap 136 and positioned forward of stationary maincontact strips 231, 232. All of the movable contacts 101, 103, 107 aremounted to contact carrier 45 that is pivotally mounted to mechanismframe 36, secured to base 26 by bolts 48. Contact carrier 45 isconnected at pivot 46 at one end of lower toggle link 43 whose other endis connected to toggle knee 41. Upper toggle link 42 extends betweenknee 41 and pivot 44 on cradle 40, with the latter being pivotallymounted at 47 to frame 36.

Transverse cradle portion 40a mounts latch plate 51, engageable bysecondary latch 53, which is connected to primary latch 65, pivoted ontrip unit frame at stub shaft 69. Primary latch is in turn engageable bythe latchplate portion of carrier 66, to maintain cradle 40 in thelatched position shown in FIG. 1, wherein circuit breaker 25 may beoperated from its open position of FIG. 1 to its closed position. Whencarrier 66 releases latch train 53, 65,the movement of cradle 40 istransmitted back through latch train 53, 65, whereby transverse pin 71is moved by primary latch 65 to pivot carrier 66 about shaft 68, therebymoving transverse common trip bar to release the latch systems of allother poles.

lnstantaneous trip means in the form of stationary magnetic framemembers 96, 98 and movable armature 78 is provided. Also provided is adelay trip means in the form of bimetal strip 77 mounted to insulatingmember on trip unit frame60.

Transverse insulation bar 147 extends through tubular members 146 at therear of each contact carrier 45 to mechanically connect the contactcarrier 45 of all poles. Aligned apertures 148 in the sides of frame 36provide clearance for movement of bar 147. Toggle 42, 43 is operated byspring means (not shown) connected between plate 39, on toggle knee 41,and the upper end of operating member 35 pivoted at its lower end toframe 36. Member 36 is connected by studs 34 to circuit breakeroperating handle 30, which is provided with stubby bifurcated extension33 extending through aperture 29 in housing cover 27. Handle extension33 mounts roller 222 that isengaged by the operating elements 235 ofauxiliary handle operating mechanism 250, having main operating handle253 for moving elements 235.

During normal operation, as movable contacts 101, 103, 107 separate fromstationary contacts 233, 231, 232 respectively, arcing will be confinedto arcing contacts 101, 233. The are formed between arcing contacts 101,233 is drawn deeply into spaced plate type arc chute 240, having upperand lower magnetic arc runners 241, 242, with the latter being securedto the upper surface of terminal strap 136 by screws 243.

In accordance with the insant invention, magnetic steel arc runner 255,secured to the upper surface of terminal strap 136 by screws 271, isdisposed immediately in front of the forward stationary main contact 231and extends into the mouth region 256 at the rear of arc chute 240,where stationary arcing contact 233 is disposed. The front edge of arcrunner 255 tapers downward from rear to front and terminates along thesides of stationary arcing contact 233.

The presence of magnetic arc runner 255 causes arcs established atstationary main contacts 231, 232 to move forward and transfer tostationary arcing contact 233 with sufficient rapidity to preventexcessive pitting of main contacts 231, 232. Once the arc transfers tostationary arcing contact 233, arc chute 240 causes the arc to beelongated and extenguished rapidly.

For those features of construction in circuit breaker 25 that have notbeen described in detail herein, reference is made to one or more of thecopending applications Ser. Nos. 275,568, 275,577, 275,446, 275,578,275,507, 275,454, 275,508, 275,621, 275,623, 275,624, 275,569, 275,522,275,521, and 275,622, all filed of even date herewith, and all assignedto the assignee of the instant invention.

Although there has been described a preferred embodiment of this novelinvention, many variations and modifications will now become apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

l. A circuit breaker comprising stationary contact means includingstationary arcing and main contact sections; movable contact meansincluding movable arcing and main contact sections operable into and outof engagement with said stationary arcing and main contact sections,respectively; arc chute means to receive and extinguish electric currentarcs drawn between said movable and stationary contact means uponseparation thereof; said stationary main contact means being disposedoutsideof said arc chute; said are chute having an entrance region; saidstationary arcing contact means being positioned at said entranceregion; and magnetic arc runner means positioned at said entrance regionand interposed between said stationary arcing and main contact sectionsto transfer arcs from said stationary main contact section to saidstationary arcing contact section and into said are chute means wherethese arcs are extinguished.

2. A circuit breaker as set forth in claim 1 also comprising anelongated terminal strap supporting on its upper surface said stationaryarcing and stationary main contact sections, with the latter beingbehind the arc chute means and the stationary arcing contact section;said are chute means extending above said terminal strap.

3. A circuit breaker as set forth in claim 2 in which the arc runnermeans is tapered downward from rear to front.

4. A circuit breaker as set forth in claim 3 in which the arc runnermeans at the rear end thereof extends across substantially the entirewidth of the terminal strap.

5. A circuit breaker as set forth in claim 4 in which the stationarymain contact section extends across substantially the entire width ofthe terminal strap.

6. A circuit breaker as set forth in claim 5 in which the stationarymain contact section includes first and second elongated portionsextending substantially across the terminal strap.

7. A circuit breaker as set forth in claim 5 in which the stationaryarcing contact section is substantially narrower than said stationarymain contact section, and the arcing runner is constructed of steel.

8. A circuit breaker as set forth in claim 2 also including additionalmagnetic arc runner means extending forward of said arcing contact meansand operatively positioned to draw arcs formed beteween separablesections of said arcing contact means deeply into said arc chute.

9. A circuit breaker as set forth in claim 2 in which said magnetic arcrunner means covers a substantial portion of sait terminal strap uppersurface in the region thereof between said stationary arcing andstationary main contact sections.

1. A circuit breaker comprising stationary contact means includingstationary arcing and main contact sections; movable contact meansincluding movable arcing and main contact sections operable into and outof engagement with said stationary arcing and main contact sections,respectively; arc chute means to receive and extinguish electric currentarcs drawn between said movable and stationary contact means uponseparation thereof; said stationary main contact means being disposedoutside of said arc chute; said arc chute having an entrance region;said stationary arcing contact means being positioned at said entranceregion; and magnetic arc runner means positioned at said entrance regionand interposed between said stationary arcing and main contact sectionsto transfer arcs from said stationary main contact section to saidstationary arcing contact section and into said arc chute means wherethese arcs are extinguished.
 2. A circuit breaker as set forth in claim1 also comprising an elongated terminal strap supporting on its uppersurface said stationary arcing and stationary main contact sections,with the latter being behind the arc chute means and the stationaryarcing contact section; said arc chute means extending above saidterminal strap.
 3. A circuit breaker as set forth in claim 2 in whichthe arc runner means is tapered downward from rear to front.
 4. Acircuit breaker as set forth in claim 3 in which the arc runner means atthe rear end thereof extends across substantially the entire width ofthe terminal strap.
 5. A circuit breaker as set forth in claim 4 inwhich the stationary main contact section extends across substantiallythe entire width of the terminal strap.
 6. A circuit breaker as setforth in claim 5 in which the stationary main contact section includesfirst and second elongated portions extending substantially across theterminal strap.
 7. A circuit breaker as set forth in claim 5 in whichthe stationary arcing contact section is substantially narrower thansaid stationary main contact section, and the arcing runner isconstructed of steel.
 8. A circuit breaker as set forth in claim 2 alsoincluding additional magnetic arc runner means extending forward of saidarcing contact means and operatively positioned to draw arcs formedbeteween separable sections of said arcing contact means deeply intosaid arc chute.
 9. A circuit breaker as set forth in claim 2 in whichsaid magnetic arc runner means covers a substantial portion of saitterminal strap upper surface in the region thereof between saidstationary arcing and stationary main contact sections.